1. Upgraded yum. Yum has been upgraded to version 2.4.x, which adds a sqlite database backend for local metadata storage. This allows yum updates to be much faster than they were previously. The following packages are added or upgraded to facilitate the new yum: createrepo, centos-yumconf, sqlite, sqlite-devel, python-elementtree, python-sqlite, python-urlgrabber, yum.

2. SystemTap. CentOS-4.2 contains a technology preview release of SystemTap. SystemTap is a dynamic system profiling framework. SystemTap is only included as a preview, and should not be used in production at this time. Please see the SystemTap website for more information:http://sourceware.org/systemtap/

3. Updated and added packages. There is a list of all packages either added or upgraded since CentOS 4.1 in the upstream release notes, please see the upstream release notes for your architecture for CentOS-4.2 on the CentOS documentation page:http://mirror.centos.org/centos/4/docs/

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ISSUES:

There is a known issue upstream when upgrading x86_64 servers. The issue seems to be related to the new audit and kernel packages when performing an upgrade. If you first install the new kernel and audit packages, then reboot and upgrade the rest of the packages, it seems to minimize this problem. Please see this bug report: http://bugs.centos.org/view.php?id=1037